Gas sealing and continuous charging method for blast furnace



1965 D. N. EVANS ETAL 3,198,623

GAS SEALING AND CONTINUOUS CHARGING METHOD FOR BLAST FURNACE Filed Sept. 1, 1961 1 2 Sheets-Sheet 1 a 4 Gi g INVENTOR-SA Doug/9K %--um 1965 D. N. EVANS ETAL 3,198,623

GAS SEALING AND CONTINUOUS CHARGING METHOD FOR BLAST FURNACE 2 Sheets-Sheet 2 Filed Sept. 1, 1961 INVE United States Patent GAS SEALING AND CONTINUOUS CHARGING NETHOD FOR BLAST FURNACE Douglas N. Evans, Ogden Dunes, and Charles D. Eider,

Gary, IntL, assignors' to Inland Steel Company, Chicago, 11]., a corporation of Delaware Filed Sept. 1, 1961, Ser. No. 135,653

4 Claims. (Cl. 75-41) The present invention relates generally to the operation of blast furnaces, and more particularly to a method which provides a gas seal at the top of the blast furnace and enables continuous charging through the furnace top.

Blast furnaces are conventionally constructed with a pair of vertically superimposed hoppers at the furnace top, each hopper being separated by a vertically movable bell-shaped first closure member, and the lower hopper being separated from the blast furnace proper by a vertically movable bell-shaped second closure member. In a typical charging operation the first closure member is opened to permit the delivery of blast furnace charging material from the upper hopper to the lower hopper, following which the first closure member is closed and the second bell-shaped closure member is opened to permit the discharge of the blast furnace charging material from the lower hopper into the blast furnace proper, and the lower closure member is then returned to the closed position. In this manner gases from the interior of the blast furnace are prevented from escaping upwardly into the upper hopper and then into the atmosphere.

Because of the interrupted batch-type charging method heretofore utilized, charging has been, of necessity, relatively complicated. In addition, the batch-type charging apparatus includes movable bell-shaped closure members and movable closure actuating members, all of these movable parts being expensive and requiring frequent periodic replacement due to the severe conditions under which they operate.

In blast furnace operation, the lower bell-shaped closure member is subjected to the abradent effect of particles in the rapidly moving dirty gas contained in the blast furnace proper, which particles cause a serious wear problem, ultimately destroying the seal formed by the closure member and causing leakage of blast furnace gas into the hoppers. This problem becomes more serious as the top pressure is increased.

All of these disadvantages are eliminated by the method of the subject invention. Essentially, the invention is performed in conjunction with apparatus which comprises an opening in the top of the blast furnace proper, open port means located above this top opening and in communication therewith, means located around the periphery of the open port means at the top thereof for directing cleaned gas downwardly through the open port means, and means for regulating the velocity pressure of the downwardly directed gas so that it is at least substantially equal to the static pressure of the gas in the blast furnace proper, thereby establishing a gas seal in the form of a clean gas-dirty gas interface at the top opening in the blast furnace.

Because no closure member is utilized to physically obstruct the top opeinng in the blast furnace, blast furnace charging material may be introduced through this top opening continuously. This is accomplished in the present invention by directing blast furnace charging material down the center or vertical axis of the open port means. The continuous movement of blast furnace charging material through the charging means and open port means also serves to impede upward movement of such blast furnace gases as might leak through the gas seal at the furnace top opening, and the above-described operation serves to impede the undesirable leakage of air from the atmosphere.

Other features and advantages are inherent in the method claimed and disclosed, as will become apparentto those skilled in the art from the following detailed description in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a diagrammatic view, in vertical section, of the upper portion of a blast furnace and of one embodiment of apparatus constructed for use with the present invent-ion;

FIGURE 2 is a fragmentary View, similar to FIGURE 1, showing a portion of another embodiment of apparatus for use with the subject invention;

FIGURE 3 is a sectional view, taken along line 3-3 in FIGURE 1 and showing one embodiment of means for directing gas downwardly into the open port; and

FIGURE 4 is a sectional view similar to FIGURE 3,

showing another embodiment of gas-directing means comprising a plurality of nozzles.

Referring initially to FIGURE 1, which illustrates one embodiment of apparatus, there is shown a blast furnace, operating at an internal pressure above atmospheric, indicated generally at 10 and having an upwardly tapering topmost wall section 11 covered by a top portion 18 having an opening 12 in communication with a gate valve housing 13 in communication with downwardly tapering open port means 19 having a lower opening 27 which extends downwardly into the gate valve housing 13. Located above open port means 19 is gas-directing means 20 having lowermost nozzle means in the form of an annular opening 21 situated around the periphery of open port means 19 and for direcitng gas downwardly into the open port means. Gas-directing means 29 is connected by conduits 22 to a blower 23 connected by a conduit 24 to means (not shown) for cleaning gas exhausted through conduits 25 at top section 11 of blast furnace 10.

Blower 23 is controlled to impart sutficient velocity and pressure to the cleaned gas so that the velocity pressure of the downwardly directed gas at blast furnace opening 12 is substantially at least equal to the static pressure of the gas within the upper section of blast furnace 10. This establishes a gas seal in the form of a clean gas-dirty gas interface at about opening 12. In this manner, dirty gas within the blast furnace proper is prevented from escaping upwardly through opening 12,, and leaves the blast furnace'proper substantially only through exhaust conduits 25 leading to the gas cleaning means. The speed of blower 23 is controlled by conventional instrumentation indicated diagrammatically at 50.

It should be noted that after the gas from the blast furnace has been cleaned, it is cooler than the gas in the blast furnace proper so that the additional heat imparted to the cleaned gas during compression will not raise the temperature of the cleaned gas to undesirable levels substantially above the temperature of the gas in the blast furnace proper.

Top opening 12 of the blast furnace is in communica tion with open port means 19 at all times during furnace operation. Although the furnace is provided with a gate valve 16, this valve is normally maintained in the open position shown in FIGURE 1, in which the gate valve 16 is enclosed in a housing portion 15. Gate valve 16 is moved to a closed position in a housing portion 14 only when it is necessary to conduct maintenance on the apparatus located above valve housing 13 or when the furnace is on bank, or during certain other non-normal conditions. Gate valve 16 is actuated by a rod 17 extending through a housing portion 26, and the rod is Operated by conventional hydraulic or mechanical means (not shown).

Because the gate valve 16 is normally maintained in an open position during operation of the blast furnace, charging material for the blast furnace can be introduced continuously into the furnace by apparatus now to be described. Extending downwardly into the top of open port means 19 is a chute into which extends a spout 32 connected to a horizontally extending conduit 33 containing a screw conveyor 34 operated by a shaft 35 connected to a motor 36 and for conveying blast furnace charging material from a hopper 37 into the spout 32. The material is introduced into hopper 37 from conveyor means 38, said material preferably being presized, premixed and properly beneficiated. Spout 32 directs blast furnace charging material delivered thereto downwardly through chute 30, through the center or vertical axis of open port means 19, through the blast furnace top opening 12 and into the blast furnace proper.-

To achieve a hot metal output from a blast furnace of approximately 2,500 tons per 24 hour day, it is necessary to introduce approximately 2.5 cubic feet per second of charging material through the blast furnace top opening 12. As the continuously introduced material passes downwardly through the open port means, additional velocity is imparted to this material bythe downward blast of cleaned gas. However, since the material strikes material of its own kind the added velocity is not particularly detrimental from the standpoint of breaking the material up into too fine a size. A continuous stream of charging material through open port means 19 also serves the additional functions of impeding the upward leakage of any blast furnace gas which may have leaked through the gas 1 seal at opening 12. Such quantities of air as may leak into the apparatus are not suflicient to cause an explosive mixture with the blast furnace gas.

Extending upwardly from chute 30 is a stack 31 having bleeder valve means 40, located at a stack top 41, and for exhausting such blast furnace gas as may enter the stack due to slips, explosions and severe unbalanced pressures. In this connection valve means 40 works in conjunction with conventional blceders (not shown) on the uptakes 25.

Referring now to FIGURE 2, there is shown another embodiment of apparatus for use with the method of the instant invention, said embodiment including downwardly and outwardly flaring bell-shaped skirt means 42 the top of which is in communication with blast furnace ,top opening 12. Skirt means 42 serves the function of mitigating the downward velocity of cleaned gas emanating from the open port means after the gas has passed furnace top opening 12, in situations wherein the velocity pressure of the cleaned gas exceeds the static pressure of the gas within the furnace interior.

FIGURE 3 shows one embodiment of gas-directing means 20, said embodiment comprising an annular lower opening 21 (FIGURE 1) defined by an inner wall 45 and an outer wall 46.

FIGURE 4 shows another embodiment of the gasdirecting means in the form of a casting 47 having a plurality of individual openings or nozzles 48 arranged around the periphery thereof at the lower extremity there- Sealing Gas Sealing Gas Sealing Gas Flow, standard Supply Pres- Velocity in c.i.n1. sure, p.s.i. Open Port,

gauge ft. per second Assuming the same 1 square foot area of opening 12, and a higher blast furnace top pressure of 10 p.s.i. gauge, a typical set of operating conditions necessary to achieve a gas seal at opening 12 are as follows:

Sealing Gas Sealing Gas Sealing Gas Flow, standard Supply Pres- Velocity in c.f.m. sure, p.s.i. Open Port,

gauge a it. per second There has thus been described a method for sealing the top of a blast furnace without the use of moving parts and which enables continuous charging of material into the blast furnace. The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as modifications will be obvious to those skilled .in the art.

What is claimed is:

1. In a method for use in conjunction with a furnace maintained at an internal pressure above atmospheric pressure and having an unobstructed upper opening through which charging material is continuously introduced into the furnace, said method preventing the escape of a first gas from within said furnace outwardly through said opening, the steps of:

continuously maintaining said opening in an open condition during the entire normal operation of the furnace;

continuously directing a stream of a second gas directly at said opening;

and controlling the velocity of said second gas so that the velocity pressure of the second gas at said opening is at least equal to the static pressure of said first gas within said furnace, to provide a gas seal at said opening in the form of a first gas-second gas interface.

2. A method for use in conjunction with a furnace maintained at an internal pressure above atmospheric pressure and having an unobstructed upper opening through which charging material is introduced into the furnace, said method preventing the escape of a first gas from within said furnace outwardly through said opening and comprising the steps of:

continuously maintaining said opening in an open condition during the entire normal operation of the furnace; continuously directing a stream of charging material downwardly through said opening; continuously directing a stream of a second gas directly at said opening simultaneous with said directing of said charging material through said opening; and controlling the velocity of said second gas so that the velocity pressure of the second gas at said opening is at least equal to the static pressure of said first gas within said furnace, to provide a gas seal at said opening in the form of a first gas-second gas interface.

3- A method as recited in claim 2 wherein:

said second gas is directed towards at least the peripheral portion of said furnace opening;

said method further comprising directing said charging material toward at least the central portion of said opening.

4. A method as recited in claim 2 and comprising:

exhausting gas from within said furnace, through another furnace opening;

cleaning said exhaust gas;

and directing at least some of said cleaned gas, as

said second gas, toward said opening.

References Cited by the Examiner UNITED ST TES PATENTS Hannes 26627 Johnson 266-27 Banes 26628 X Hechenbleikner 759 Burgoyne et al. 266-28 Carter 26638 Mohr et al. 26627 Thornhill et a1 266-20 Pieterse 110104 MORRIS O. WOLK, Primary Examiner.

15 RAY K. VVINDHAM, Examiner. 

1. IN A METHOD FOR USE IN CONJUNCTION WITH A FURNACE MAINTAINED AT AN INTERNAL PRESSURE ABOVE ATMOSPHERIC PRESSURE AND HAVING AN UNOBSTRUCTED UPPER OPENING THROUGH WHICH CHARGING MATGERIAL IS CONTINUOUSLY INTRODUCED INTO THE FURNACE, SAID METHOD PREVENTING THE ESCAPE OF A FIRST GAS FROM WITHIN SAID FURNACE OUTWARDLY THROUGH SAID OPENING, THE STEPS OF: CONTINUOUSLY MAINTAINING SAID OPENING IN AN OPEN CONDITION DURING THE ENTIRE NORMAL OPERATION OF THE FURNACE; CONTINUOUSLY DIRECTING A STREAM OF A SECOND GAS DIRECTLY AT SAID OPENING; AND CONTROLLING THE VELOCITY OF SAID SECOND GAS SO THAT THE VELOCITY PRESSURE OF THE SECOND GAS AT SAID OPENING IS AT LEAST EQUAL TO THE STATIC PRESSURE OF SAID FIRST GAS WITHIN SAID FURNACE, TO PROVIDE A GAS SEAL AT SAID OPENING IN THE FORM OF A FIRST GAS-SECOND GAS INTERFACE. 